1. Field of the Invention
The present invention relates to a method for producing a liquid crystal device, particularly to a method for producing a liquid crystal device having active elements provided with insulation films formed by anodic oxidation.
2. Description of Related Art
Liquid crystal devices provided with active elements like elements having a non-linear voltage current characteristic, for example TFT (Thin Film Transistor) or TFD (Thin Film Diode) for each pixel are commercially available conventionally. Some of these kinds of liquid crystal devices contain active elements constructed by forming anodic oxidation films during the manufacturing process on the surface of the electrode sections to serve as insulation films.
One example of the active element described above is a diode element (referred to a MIM element hereinafter) provided with a laminated structure unit of MIM (Metal-Insulator-Metal). This MIM element is formed by forming an insulation film on the surface of a first electrode layer formed of an electric conductor by anodic oxidation followed by additionally forming a second electrode layer thereon. In this case, using the anodic oxidation for forming the insulation film allows an insulation film having a uniform thickness along with having a good reproducibility to be formed with reduced production cost. Moreover, characteristics of the element may be securely stabilized since the film quality can be readily improved by applying an annealing treatment or the like.
Examples of the method for producing the MIM element with the foregoing construction includes the following steps. An underlayer consisting of Ta2O5 is at first formed on a glass substrate in full measure followed by forming an energizing pattern including a pluraity of the first electrode layers on this underlayer using Ta. This energizing pattern is in advance formed into a pattern similar to the wiring layer. An insulation film consisting of Ta2O5 is then formed on each first electrode layer formed for each pixel via the energizing pattern. In the next step, the MIM element is formed by forming the second electrode layer consisting of Cr so that the layer is partly overlapped on the insulation film or the first electrode layer. Finally, a transparent pixel electrode consisting of ITO (Indium Tin Oxide) is formed so that the electrode is electrically connected to the second electrode layer.
Meanwhile, an energizing pattern formed on the surface of the substrate for respective pixels for energizing through all the plurality of first electrode layers should be formed prior to the anodic oxidation step in the liquid crystal device provided with the conventional MIM elements as described above. The energizing pattern is formed into a pattern having the same shape as the finally formed wiring layer when this energizing pattern is used for the wiring layer while, when the energizing pattern is not directly used as the wiring layer, the pattern is formed into a pattern almost identical with the wiring layer along the region for forming the wiring layer in order to accommodate the energizing path in the element.
However, once a part of the energizing pattern is broken, no insulation layer is formed on the surface of the respective first electrodes located at the tip of the broken part, thereby causing a problem that incomplete MIM elements are formed. When a pattern having a partially defective shape, though the pattern is not broken, is formed, resistance of the feeding path is locally increased on the time of anodic oxidation to make the variation of the thickness of the insulation film or the like, non-uniform with distributed characteristics of the active elements, thereby causing a problem that the display quality is deteriorated.
On the other hand, in the energizing pattern, while a part of a plurality of stripe-shaped wiring pattern sections aligned in parallel with each other in the interior of the liquid crystal display region as the wiring layer usually has a construction in which the wiring pattern sections are joined with each other by the joint pattern sections for putting them into continuity t outside of the liquid crystal display region, this joint pattern section is usually cut off from the wiring pattern section after completing the liquid crystal cell by breaking the substrate. However, an electric impulse is imparted to a plurality of the MIM elements via the joint pattern section when, for example, the insulation layer to be formed on the uppermost layer of the element substrate is formed by sputtering before the joint pattern section is cut of, causing a problem that the MIM element is broken by the process damage during the step described above.
Accordingly, the object of the present invention is to solve the problems hitherto described, to avoid defective anodic oxidation in the method for producing the liquid crystal device even when breaking of the energizing pattern has taken place or the pattern shape becomes imperfect, along with providing a novel producing method for allowing the process damage of the MIM element to be decreased.
The present invention, carried out for solving the foregoing problems, provides a method for producing a liquid crystal device having a plurality of wiring layers, pixel electrodes formed for each pixel and active elements provided with insulation films connected between the wiring layer and the pixel electrode and being formed by anodic oxidation on electric conductors on one of the two substrates sandwiching a liquid crystal layer, providing the steps of:
forming an energizing pattern on the substrates including the electric conductor and connecting the electric conductor so as to be able to energize from a plurality of continuity paths;
forming an insulation film by anodic oxidation on the electric conductor by energizing through the energizing pattern; and
eliminating a part of the energizing pattern so as to cut off at least one of the a plurality of the continuity paths in the energizing pattern.
According to the method for producing the liquid crystal device, insulation films can be formed on the electric conductors through another continuity path even when one continuity path is cut off or made to have a high resistance due to wire breakage or occurrence of imperfect shapes in a part of the energizing pattern during anodic oxidation since the energizing pattern allows an electric conductor to energize through a plurality of the continuity paths. Accordingly, defective insulation films are hardly formed and production yield of the liquid crystal device is increased, thus improving the display quality of the liquid crystal device.
It is preferable in the step for eliminating a part of the energizing pattern that the energizing pattern is eliminated so as to cut off another continuity path not belonging to the continuity paths of the energizing patterns for finally connecting the wiring layers and the active elements.
According to the method described above, the element side substrate can be constructed as usual by cutting off the another unnecessary continuity paths finally after applying anodic oxidation through the energizing pattern.
The method for producing a liquid crystal device according to the present invention comprises the step for forming an underlayer on the surface of the substrate in advance to the step for forming the energizing pattern and it is preferable in the foregoing step for eliminating a part of the energizing pattern that the underlayer is selectively eliminated in the area for forming the pixel electrodes.
According to the method described above, it is possible to improve the contrast of the liquid crystal device since light transmittance of the pixel region can be enhanced by eliminating the region for forming the pixel electrodes in the underlayer to form an opening port-ion or by making the underlayer thin in the step for eliminating a part of the energizing pattern.
It is preferable in the step for eliminating a part of the enerigizng pattern that a part of the energizing pattern is eliminated so that the electric conductors corresponding to the active elements to be connected to the mutually different wiring layers are not electrically connected with each other.
According to the production method described above, possible risks for the active elements to be subjected to electrostatic breakage during some processing steps after completion of the active elements can be reduced by eliminating the portions joining among the wiring layers.
The present invention provides a method for producing a liquid crystal device in which substrates for the respective liquid crystal devices are produced by forming a plurality of wiring layers, pixel electrodes to be disposed for each pixel and active elements being electrically connected between the wiring layer and the pixel electrode and provided with an insulation film formed by anodic oxidation of the electric conductor, on a parent material substrate provided on one of the substrates for a plurality of liquid crystal devices, followed by cutting off the parent material substrate, the production method preferably provides the steps of:
forming a first energizing pattern for electrically connecting the electric conductors on the substrate for a plurality of the liquid crystal devices with each other and a second energizing pattern for electrically connecting the electric conductors formed on the substrates of the respective liquid crystal devices with each other; and
forming an insulation film by anodic oxidation on the electric conductors of a plurality of the liquid crystal devices by energizing through the energizing pattern.
According to the method of the present invention, forming the first energizing pattern for connecting among the electric conductors on the substrates of a plurality of the liquid crystal devices so as to be able to energize and the second energizing pattern for connecting among the electric conductors formed on the substrates of respective liquid crystal devices so as to be able to energize allows the second energizing pattern to energize through the electric conductors on the substrates of respective liquid crystal devices even when some abnormal wiring such as wire breaking has occurred in the first energizing pattern, thereby enabling to constantly form the active elements for use in a plurality of the liquid crystal devices.
It is preferable that the second energizing patterns are provided outside of the area for forming the pixel electrodes, followed by the step for eliminating the second energizing patterns along with providing a step for forming the pixel electrodes.
According to the method as described above, providing the second energizing pattern outside of the area for forming the pixel electrodes prevents the area for forming the pixel electrodes from being damaged in the step for eliminating the second energizing pattern. Consequently, the electric conductors on the substrates of respective liquid crystal devices are enabled to energize through the second energizing pattern while keeping the patterning accuracy of the-pixel electrodes even when some abnormal wiring such as wire breaking has occurred in the first energizing pattern, allowing the active elements of a plurality of the liquid crystal devices to be constantly formed.